The present invention relates to an arrangement for controlling temperature of intake air of an internal-combustion engine, comprising an intake air filter having an untreated-air connection piece, a cold-air duct and a hot-air duct, a control valve swivellably arranged in the untreated-air connection piece, a pneumatic actuator operatively coupled to the control valve to adjust the control valve as a function of the temperature of air fed to the internal-combustion engine, and a thermostat subjected to cold air, the thermostat being coupled to a movable stop that determines a swivel range of the control valve in a direction which closes off the warm-air duct.
An arrangement of the above-mentioned type is known from German Patent Document DE-PS 26 24 210. This arrangement has the purpose of maintaining the temperature of the intake air within a defined range and comprises a pneumatic actuator which is controlled by a temperature sensor in the form of a bimetallic element.
When the main throttle valve is opened, as in the case of full-load operating conditions, an internal-combustion engine must take in colder air so that a better filling ratio and a higher performance can be achieved. However, the disadvantage exists here that during a full-load, irrespective of the existing temperatures, only cold air is taken in. In particular, at a temperature which is slightly above the freezing point, the intake branch may freeze up which results in a considerable power reduction of the internal-combustion engine. In order to prevent this, a thermostat is provided which is subjected to cold air and which determines the swivel range of the control valve in the direction which closes off the warm-air duct. This means that, even in the case of a full load, particularly in the critical temperature range, the cold air is mixed at least with a small amount of warm air.
It is a disadvantage of the known arrangement that the thermostat must be adjusted in a high-expenditure manner in order to achieve an optimal characteristic control curve.